| |
| // (C) Copyright Rani Sharoni 2003. |
| // Use, modification and distribution are subject to the Boost Software License, |
| // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt). |
| // |
| // See http://www.boost.org/libs/type_traits for most recent version including documentation. |
| |
| #ifndef BOOST_TT_IS_BASE_AND_DERIVED_HPP_INCLUDED |
| #define BOOST_TT_IS_BASE_AND_DERIVED_HPP_INCLUDED |
| |
| #include <ndnboost/type_traits/intrinsics.hpp> |
| #ifndef BOOST_IS_BASE_OF |
| #include <ndnboost/type_traits/is_class.hpp> |
| #include <ndnboost/type_traits/is_same.hpp> |
| #include <ndnboost/type_traits/is_convertible.hpp> |
| #include <ndnboost/type_traits/detail/ice_and.hpp> |
| #include <ndnboost/config.hpp> |
| #include <ndnboost/static_assert.hpp> |
| #endif |
| #include <ndnboost/type_traits/remove_cv.hpp> |
| |
| // should be the last #include |
| #include <ndnboost/type_traits/detail/bool_trait_def.hpp> |
| |
| namespace ndnboost { |
| |
| namespace detail { |
| |
| #ifndef BOOST_IS_BASE_OF |
| #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x581)) \ |
| && !BOOST_WORKAROUND(__SUNPRO_CC , <= 0x540) \ |
| && !BOOST_WORKAROUND(__EDG_VERSION__, <= 243) \ |
| && !BOOST_WORKAROUND(__DMC__, BOOST_TESTED_AT(0x840)) |
| |
| // The EDG version number is a lower estimate. |
| // It is not currently known which EDG version |
| // exactly fixes the problem. |
| |
| /************************************************************************* |
| |
| This version detects ambiguous base classes and private base classes |
| correctly, and was devised by Rani Sharoni. |
| |
| Explanation by Terje Slettebo and Rani Sharoni. |
| |
| Let's take the multiple base class below as an example, and the following |
| will also show why there's not a problem with private or ambiguous base |
| class: |
| |
| struct B {}; |
| struct B1 : B {}; |
| struct B2 : B {}; |
| struct D : private B1, private B2 {}; |
| |
| is_base_and_derived<B, D>::value; |
| |
| First, some terminology: |
| |
| SC - Standard conversion |
| UDC - User-defined conversion |
| |
| A user-defined conversion sequence consists of an SC, followed by an UDC, |
| followed by another SC. Either SC may be the identity conversion. |
| |
| When passing the default-constructed Host object to the overloaded check_sig() |
| functions (initialization 8.5/14/4/3), we have several viable implicit |
| conversion sequences: |
| |
| For "static no_type check_sig(B const volatile *, int)" we have the conversion |
| sequences: |
| |
| C -> C const (SC - Qualification Adjustment) -> B const volatile* (UDC) |
| C -> D const volatile* (UDC) -> B1 const volatile* / B2 const volatile* -> |
| B const volatile* (SC - Conversion) |
| |
| For "static yes_type check_sig(D const volatile *, T)" we have the conversion |
| sequence: |
| |
| C -> D const volatile* (UDC) |
| |
| According to 13.3.3.1/4, in context of user-defined conversion only the |
| standard conversion sequence is considered when selecting the best viable |
| function, so it only considers up to the user-defined conversion. For the |
| first function this means choosing between C -> C const and C -> C, and it |
| chooses the latter, because it's a proper subset (13.3.3.2/3/2) of the |
| former. Therefore, we have: |
| |
| C -> D const volatile* (UDC) -> B1 const volatile* / B2 const volatile* -> |
| B const volatile* (SC - Conversion) |
| C -> D const volatile* (UDC) |
| |
| Here, the principle of the "shortest subsequence" applies again, and it |
| chooses C -> D const volatile*. This shows that it doesn't even need to |
| consider the multiple paths to B, or accessibility, as that possibility is |
| eliminated before it could possibly cause ambiguity or access violation. |
| |
| If D is not derived from B, it has to choose between C -> C const -> B const |
| volatile* for the first function, and C -> D const volatile* for the second |
| function, which are just as good (both requires a UDC, 13.3.3.2), had it not |
| been for the fact that "static no_type check_sig(B const volatile *, int)" is |
| not templated, which makes C -> C const -> B const volatile* the best choice |
| (13.3.3/1/4), resulting in "no". |
| |
| Also, if Host::operator B const volatile* hadn't been const, the two |
| conversion sequences for "static no_type check_sig(B const volatile *, int)", in |
| the case where D is derived from B, would have been ambiguous. |
| |
| See also |
| http://groups.google.com/groups?selm=df893da6.0301280859.522081f7%40posting. |
| google.com and links therein. |
| |
| *************************************************************************/ |
| |
| template <typename B, typename D> |
| struct bd_helper |
| { |
| // |
| // This VC7.1 specific workaround stops the compiler from generating |
| // an internal compiler error when compiling with /vmg (thanks to |
| // Aleksey Gurtovoy for figuring out the workaround). |
| // |
| #if !BOOST_WORKAROUND(BOOST_MSVC, == 1310) |
| template <typename T> |
| static type_traits::yes_type check_sig(D const volatile *, T); |
| static type_traits::no_type check_sig(B const volatile *, int); |
| #else |
| static type_traits::yes_type check_sig(D const volatile *, long); |
| static type_traits::no_type check_sig(B const volatile * const&, int); |
| #endif |
| }; |
| |
| template<typename B, typename D> |
| struct is_base_and_derived_impl2 |
| { |
| #if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000) |
| #pragma warning(push) |
| #pragma warning(disable:6334) |
| #endif |
| // |
| // May silently do the wrong thing with incomplete types |
| // unless we trap them here: |
| // |
| BOOST_STATIC_ASSERT(sizeof(B) != 0); |
| BOOST_STATIC_ASSERT(sizeof(D) != 0); |
| |
| struct Host |
| { |
| #if !BOOST_WORKAROUND(BOOST_MSVC, == 1310) |
| operator B const volatile *() const; |
| #else |
| operator B const volatile * const&() const; |
| #endif |
| operator D const volatile *(); |
| }; |
| |
| BOOST_STATIC_CONSTANT(bool, value = |
| sizeof(bd_helper<B,D>::check_sig(Host(), 0)) == sizeof(type_traits::yes_type)); |
| #if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000) |
| #pragma warning(pop) |
| #endif |
| }; |
| |
| #else |
| |
| // |
| // broken version: |
| // |
| template<typename B, typename D> |
| struct is_base_and_derived_impl2 |
| { |
| BOOST_STATIC_CONSTANT(bool, value = |
| (::ndnboost::is_convertible<D*,B*>::value)); |
| }; |
| |
| #define BOOST_BROKEN_IS_BASE_AND_DERIVED |
| |
| #endif |
| |
| template <typename B, typename D> |
| struct is_base_and_derived_impl3 |
| { |
| BOOST_STATIC_CONSTANT(bool, value = false); |
| }; |
| |
| template <bool ic1, bool ic2, bool iss> |
| struct is_base_and_derived_select |
| { |
| template <class T, class U> |
| struct rebind |
| { |
| typedef is_base_and_derived_impl3<T,U> type; |
| }; |
| }; |
| |
| template <> |
| struct is_base_and_derived_select<true,true,false> |
| { |
| template <class T, class U> |
| struct rebind |
| { |
| typedef is_base_and_derived_impl2<T,U> type; |
| }; |
| }; |
| |
| template <typename B, typename D> |
| struct is_base_and_derived_impl |
| { |
| typedef typename remove_cv<B>::type ncvB; |
| typedef typename remove_cv<D>::type ncvD; |
| |
| typedef is_base_and_derived_select< |
| ::ndnboost::is_class<B>::value, |
| ::ndnboost::is_class<D>::value, |
| ::ndnboost::is_same<ncvB,ncvD>::value> selector; |
| typedef typename selector::template rebind<ncvB,ncvD> binder; |
| typedef typename binder::type bound_type; |
| |
| BOOST_STATIC_CONSTANT(bool, value = bound_type::value); |
| }; |
| #else |
| template <typename B, typename D> |
| struct is_base_and_derived_impl |
| { |
| typedef typename remove_cv<B>::type ncvB; |
| typedef typename remove_cv<D>::type ncvD; |
| |
| BOOST_STATIC_CONSTANT(bool, value = (BOOST_IS_BASE_OF(B,D) && ! ::ndnboost::is_same<ncvB,ncvD>::value)); |
| }; |
| #endif |
| } // namespace detail |
| |
| BOOST_TT_AUX_BOOL_TRAIT_DEF2( |
| is_base_and_derived |
| , Base |
| , Derived |
| , (::ndnboost::detail::is_base_and_derived_impl<Base,Derived>::value) |
| ) |
| |
| #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
| BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_2(typename Base,typename Derived,is_base_and_derived,Base&,Derived,false) |
| BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_2(typename Base,typename Derived,is_base_and_derived,Base,Derived&,false) |
| BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_2(typename Base,typename Derived,is_base_and_derived,Base&,Derived&,false) |
| #endif |
| |
| #if BOOST_WORKAROUND(__CODEGEARC__, BOOST_TESTED_AT(0x610)) |
| BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_1(typename Base,is_base_and_derived,Base,Base,false) |
| #endif |
| |
| } // namespace ndnboost |
| |
| #include <ndnboost/type_traits/detail/bool_trait_undef.hpp> |
| |
| #endif // BOOST_TT_IS_BASE_AND_DERIVED_HPP_INCLUDED |